String theorists need to do much more to explain their field’s genuine links to experiment

String theory’s lack of falsifiability is minimized as a problem, and the fact that it “raises several philosophical issues, such as the role of anthropic reasoning” is listed as a point in its favor. As for those who complain that string theory predicts nothing, in particular nothing about what will happen at the LHC, they are told to just shut up:

With CERN’s Large Hadron Collider (LHC) due to switch on next year, now is the wrong time to slam string theory for its lack of predictive power. While not able to prove string theory is right, the discovery of supersymmetric particles at the LHC would give it a major boost…

The fact that string theory doesn’t predict supersymmetry visible at LHC scales is actually acknowledged in the advertising supplement by Kachru and Susskind.

The few quotes from string theory skeptics allowed seem chosen to be those that put string theory in the most favorable possible light (except for Phil Anderson, who is reduced to hostile spluttering by Polchinski’s claims that string theory may explain high Tc superconductivity). This allows the editorialist to conclude:

However, the richness of string theory that has become apparent in the last decade, and its increasing contact with the real world, gives theorists something to shout about. This is why our main feature on the subject, which started with fairly modest intentions, has ballooned into the longest ever to appear in Physics World. As the views of even many non-string theorists in the article make clear, the theory still holds all the potential it ever did to revolutionize our understanding of the universe.

The critique of string theory by Smolin and myself is pretty much completely ignored or dismissed, with Susskind quoted as having come up with a new insulting term for us (to him we’re “Smoit”, evidently he likes that better than the “Swolin” favored by those in Santa Barbara). The claim is made that

few string theorists think that the sometimes negative portrayal of string theory in the popular arena recently has had much of an effect other than to irritate people.

Amidst the endless misleading hype contained in the Physics World piece, there’s some that simply is demonstrably completely untrue. The most egregious example might be the discussion of Witten’s Fields Medal which claims that it was awarded him due to his work on string theory compactification spaces:

.. with the study of 6D “Calabi–Yau” spaces making Witten in 1990 the first physicist to be awarded the prestigious Fields Medal

The quotes from Witten himself don’t include any of the hype about connections to experiment. He describes string theory as something very poorly understood, with even the fundamental equations of the theory unknown, and no good ideas about how to find them, leading to the danger that even if his vision is correct, realizing it may just be too hard:

It’s incredibly rich and mostly buried underground. People just know bits and pieces at the surface or that they’ve found by a little bit of digging, even though this so far amounts to an enormous body of knowledge… There is an incredible amount that is understood, an unfathomable number of details. I can’t think of any simple way of summarizing this that will help your readers. But despite that, what’s understood is a tiny, tiny amount of the full picture.. One of the greatest worries we face is that the theory may turn out to be too difficult to understand… [about the search for equations for string theory] This is certainly a question that interests me… but if I don’t work on it all the time, it’s because it’s difficult to know how to make progress.

Unlike Witten, many of the other string theorists quoted seem to have no problem with issuing streams of highly misleading hype claiming “predictions” of string theory. For instance, from David Gross:

String theory is full of qualitative predictions, such as the production of black holes at the LHC or cosmic strings in the sky, and this level of prediction is perfectly acceptable in almost every other field of science,” he says. “It’s only in particle physics that a theory can be thrown out if the 10th decimal place of a prediction doesn’t agree with experiment.

I don’t know how to characterize this kind of claim that string theory is as predictive as other scientific theories, just not able to get accuracy to 10 decimal places, as anything other than out-and-out dishonesty. If someone could come up with a legitimate, distinctive, testable prediction of string theory that gave even the correct order of magnitude for some experimental result, that would be a huge breakthrough.

Michael Green, while describing the landscape and its potential to allow for a small CC as “an enormous success” for string theory, is one of several string theorists characterizing the status of string theory as being just as good as that of QFT, with the landscape not a real problem at all, just a “supposed” one:

This supposed problem with a theory having many solutions has never been a problem before in science.

Several people promote the anthropic point of view, with Susskind describing it as the third superstring revolution, one that is even more of a revolution than the others. Polchinski adds

In terms of changing the way we think about the world, the anthropic landscape is certainly as big as the other revolutions

while Susskind’s colleague Shamit Kachru is described as “in the middle”, sensibly pointing out that it would have been a stupid thing for people to do, once they realized that the ratios of sizes of planetary orbits were environmental, to start claiming that “there is a deep anthropic lesson to be learned from Newtonian gravity.”

All in all, I think that the picture the Physics World article presents of the reaction of leading string theorists to the failure of the superstring unification project is a depressing one. Instead of acknowledging in any way this failure and considering what can be learned from it, on the whole they seem to prefer to abandon science for anthropic pseudo-science, to spout misleading claims of bogus “predictions” of string theory, and make indefensible claims that the lack of predictivity of string theory is not unusual for a science.

On the other hand, among string theory skeptics, I fear that the attitude of Howard Georgi is all too common:

I have been critical in the past of some of the rhetoric used by string-theory enthusiasts,” says Howard Georgi of Harvard University, who coinvented the supersymmetric extension of the Standard Model in 1981. “But I think that this problem has largely corrected itself as string theorists learned how complicated string theory really is. I am concerned about the focus of young theorists on mathematical details, rather than what I would consider the real-world physics of scattering experiments, but with any luck the LHC will take care of that by reminding people how interesting the real world can be.”

The problem with string theory is not too much mathematics and a lack of effort towards making connection to real world experiments, but that it is a wrong idea about unification, and thus cannot ever explain the standard model or predict what lies beyond it. The recent move among string theorists to hype bogus claims about connections to experiment, abandoning the search for greater mathematical insight into string theory as just “too hard”, retooling themselves as more salable “string phenomenologists” and “string cosmologists” is not a healthy trend. It is based on adopting the Susskind-Polchinski “multiverse” revolution in the received wisdom about how to do fundamental physics, slowly turning a once great subject from a science into a pseudo-science.

Update: Lubos is beside himself with glee over the Physics World article, see here and here (don’t miss the photo-shopped “Smoit” graphic of me and Lee Smolin). For something more reasoned, there’s a short piece at Wired.

134 Responses to This Month’s Hype

If you can produce a reference from the period before the top quark mass was measured in which a supersymmetry advocate said that supersymmetry was wrong if the top quark was not in a definite mass range (rather than just that one of many supersymmetry scenarios gave a possible mass range), please do so.

and various successor papers. Also you might have a look at a textbook published in 1989, ‘Particle Physics and Cosmology’ by Collins, Martin and Squires, or the popular science book by Gordon Kane on supersymmetry.

This work on dynamical electroweak symmetry breaking in no scale supergravity is very well known. In fact, all computer programs such as Isajet, SuSpect, etc. which calculate the Higgs mass and low energy superpartner spectrum use this.

Sorry, but you are really wasting my time. I made the mistake of looking at the paper you mention. It doesn’t contain anything like what I asked for. It’s just the same sort of unsuccessful model that you are now, a quarter century later, still working on, and still promoting as “supersymmetry predicts the fermion masses”. This wasn’t true then, and it isn’t true now, for reasons that people have repeatedly pointed out to you.

Peter,
You should be embarassed by your complete ignorance of particle physics and phenomenology. This is a very basic result which is widely used in just about every calculation used today and for you to not even be aware of it is apalling.

I’m not ignorant of that calculation, I just don’t think it’s compelling evidence for SUSY. I asked you to provide a reference claiming that this was a definite prediction of SUSY (as opposed to something model-dependent), and you responded by quoting something that doesn’t do this at all and continuing to insult me. If you were arguing against string theory I would long ago have put you on my block list as someone ill-informed who added nothing but misinformation and/or hostility to the comment section here. Since I don’t want to be accused of censorship, I guess I’ll continue to allow your misinformation and stupid personal attacks to appear here. But you’re really not doing a good job of representing advocacy for string theory…

Peter,
You’re just playing games to avoid having to concede the point on this issue. Everyone knowledgable knows this result and it is a standard (generic) part of SUSY phenomenology. For the record, I do have a Ph.D. in high-energy physics and am intimately familiar with the current status of the subject. Certainly, more so than you.

On the subject of personal attacks, I seem to recall being rererred to by you a few comments back as a troll. Care to answer for that?

Peter,
I hardly think pointing out errors in your statements as deliberately posting comments to stir up controversy. The fact remains that you don’t seem to be aware of basic developments in a subject for which you pass yourself off as an expert. Dyanmical electroweak symmetry breaking is just one example. You argument regarding gauge coupling unification is also completely wrong. It’s hard to say whether you just don’t know what you’re talking about or if you’re just fundamentally dishonest, but the net result is that many people end up being mislead by your comments.

Peter:”If you can produce a reference from the period before the top quark mass was measured in which a supersymmetry advocate said that supersymmetry was wrong if the top quark was not in a definite mass range (rather than just that one of many supersymmetry scenarios gave a possible mass range), please do so.”

I think that the answer is obvious in the context of MSSM. Indeed, if the top were light, there would be no REWSB and extra stuff would have to be added to the MSSM to accomplish this. And indeed, all the standard MSSM packages automatically incorporate this to generate the higgs mass etc.

Eric, Peter has asked you a carefully worded question to which there is an obvious answer – “many supersymmetric scenarious”, whatever they are, don’t predict a heavy top.

Supersymmetry by itself is just a framework and, of course, such a specific prediction (heavy top) without a concrete model is impossible and Peter knows this and that’s why he asked you this ridiculous question.

Alex,
Yes, I know that Peter was just playing word games to avoid the issue. The bottom line is that in the MSSM and similar models, the electroweak symmetry breaking scale is determined dynamically. For this to work a large top mass is required, and this was realized in the 80’s long before the top was discovered. Peter’s tactic is to play ignorant and try to obfuscate because he knows that this completely undermines his arguments that there is no evidence for SUSY.

“I can construct supersymmetric models in which the top quark must be heavy. Therefore supersymmetry requires a heavy top quark”. If a child presented you with this kind of reasoning then you might feel duty bound to correct them. I certainly would. The fact it seems to be perfectly acceptable amongst particle physicists now just shows how far the subject has fallen. It seems that what was once the hardest of hard sciences is now just a mushy neverland where optimism matters more than fact, hype more than reasoning, and who you suck up to more than the substance of your research. You are welcome to it. All of it.

Dear Peter and Chris,
You guys are really into convoluted bs and self-deception. What we’re talking about it the MSSM, and a heavy top mass is required in the MSSM to radiatively break the electroweak symmetry. I’m not sure what other supersymmetric models you’re talking about that wouldn’t require a heavy top. Any model which includes the standard model and TeV scale supersymmetry will have this feature. So, stopping misleading yourselves and others with your desperate attempts to deny any evidence for supersymmetry. It’s just sad.

Peter,
What Alex has said is incorrect. It is simply not true that many supersymmetric scenarios don’t predict a heavy top. Well, it might be true if that scenario does not include electroweak symmetry breaking or if your model doesn’t include TeV scale SUSY or the standard model.
For your reference, here are publications you should look at if you want to educate yourself:

As Alex pointed out, this is a standard, generic feature of SUSY phenomenology and is a feature of every computer program used to obtain low-energy SUSY and Higgs spectra. Why do you suppose the uncertainty in the top mass is so important in calculating the expected Higgs mass?

Again, I would expect any real particle physicist to be well aware of this, so either there are large holes in your education or you are deliberately being deceptive.

You just continue to do the same thing endlessly: posting comments that are a combination of insults and misinformation. Alex, who I suspect has no great sympathy for my point of view, has tried to politely explain to you that you’re wrong. Maybe someone else wants to try their hand at this, but it’s rather obviously a complete waste of time.

This discussion is ridiculous. The physics here is quite simple: if you start out with non-tachyonic masses for the Higgses in the MSSM, you have to drive one of them tachyonic to get EWSB. How can that happen? Well, if you look at the RGEs, it’s the contributions from Yukawas that push the mass terms toward being tachyonic. So yes, you need some large Yukawas to get radiative EWSB. No one disagrees with that, right? Anything else is semantics.

Eric, I just wanted say that you fell into Peter’s trap by using the loose language and saying that the heavy top is evidence for supersymmetry while referring to the MSSM. We all know you were not talking about N=4 SYM when you referred to supersymmetric models. The bottom line is that there is plenty of indirect evidence for MSSM and it will be exciting when the superpartners are discovered.

Eric, I have a question to you since we’re having this discussion. If you take split SUSY with scalar masses at about the GUT scale or slightly lower, is there enough RGE running to drive (m_hu)^2 negative? If not, how do they achieve EWSB?

Alex,
I’m not an expert on split SUSY, and where I come from we would not discuss such models in polite company, but here goes. My understanding is that they use the ‘little Higgs’ mechanism where strong dynamics at some high (few TeV) scale are employed a la technicolor for EWSB. Such models also give up solving the hierarchy problem, although they can apparently manage to maintain gauge coupling unification. In my humble opinion, split SUSY is very contrived and artificial which is the result of giving up a large amount of SUSY.

Of course you could always consider super split supersymmetry, which would have no way of explaining the top mass, EWSB, or the hierarchy problem, since this is just the normal standard model. Peter Woit would probably use this an example where a supersymmetric model doesn’t predict a large top mass. 😉

if we conducted a poll among the CDF and D0 collaborations that discovered the top and measured its mass for the first time, how many of them, do you think, would be convinced that the top quark mass was predicted by SUSY theorists before their discovery?

Anghe,
Most CDF and D0 colloboraters would agree that a large top mass was anticipated from radiative EWSB, and the fact that the top turned out to have such a large mass as one of the reasons for them to pay attention to SUSY.

My understanding is that they use the ‘little Higgs’ mechanism where strong dynamics at some high (few TeV) scale are employed a la technicolor for EWSB.

Your understanding is completely wrong. (Doesn’t anyone ever look things up before talking about them on a blog?) If you want supersymmetric-looking unification with a split spectrum in a natural theory, you might try something like that. But split supersymmetry is just the MSSM with a split spectrum.

Have you checked this with “most CDF and DO collaborators”? Just a wild guess, but I would suspect that they might tell you that a “large” top mass was anticipated not because of SUSY, but because the top was not seen at “low” mass.

Anon,
I think it would depend on the amount of splitting in the spectrum. I’m sure there are split models where you can get EWSB and others where it isn’t possible and you need something else. In any case, split SUSY is inherently unnatural since I can’t think of any reason why some supersymmetric partners would have large GUT scale masses and others wouldn’t. This only works if you believe in fine-tuning which leads you to anthropic reasoning.

Peter,
The several CDF and D0 collaborators that I know as well as those at CERN were well aware that a large top mass was anticipitated by SUSY. As has been pointed out to you now by several people, this is a very well known result. Using exactly the same idea it’s pretty easy to calculate that the Higgs mass should be in the range 114-121 GeV using the current top mass of 170.9 +/- 1.8 GeV. All of the experimentalists know this.